A novel AFNCS algorithm for super-resolution SAR in curve trajectory
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A novel AFNCS algorithm for super‑resolution SAR in curve trajectory Tan Qu1 · Yan Zhang2 · Jiaji Wu1 Received: 15 July 2020 / Accepted: 29 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract With the improvement of SAR resolution, super-resolution SAR imaging is more and more widely used in the all-time and all-weather video surveillance and remote sensing imaging. One implementation of super-resolution SAR is that radar works in the spotlight mode. In the case with highly squinted angle and acceleration, the azimuth space variance and the coupling between range and azimuth will become serious in super-resolution imaging. Thus, an azimuth frequency nonlinear chirp scaling algorithm is proposed to solve this problem. Based on the acceleration model, the accurate 2-D spectrum is performed by adopting the method of series reversion. The space-variance of missile-borne SAR in curved flight path is analyzed and an azimuth polynomial phase filter is constructed to make the coefficients of the perturbation function has sufficient flexibility to eliminate the spatial-variant couple terms between range and azimuth. In addition, the gradient operation is used to expand the space-variant coefficients of azimuth modulation term, and the perturbation function is applied to eliminate the space-variant in azimuth direction. The proposed focusing method can process the missile-borne SAR data obtained in spotlight mode in highly squinted angle with high efficiency. The simulation results verify the effectiveness of the proposed imaging approach. The integration of the research in this paper and the deep learning will further pave the way of superresolution SAR imaging applications in disaster monitoring, security and surveillance. Keywords Spotlight SAR · Super-resolution · Azimuth frequency nonlinear chirp scaling · Curve trajectory
1 Introduction While moving towards to multi-mode, multi-band and multipolarization, how to improve the resolution is always an important development direction in synthetic aperture radar (SAR) imaging field [1–3]. The resolution of SAR imaging has also developed from low resolution to super-resolution. For missile-borne SAR, high-resolution or super-resolution imaging of the region is always necessary to obtain the accurate targets position, and super-resolution of the interested regions image is usually implemented through the spotlight mode, because the control beam always points to the center of the imaging area and increases the synthetic aperture time during the process of imaging in spotlight mode, and thus high azimuth resolution, even super-resolution in azimuth * Yan Zhang [email protected] 1
School of Electronic Engineering, Xidian University, Xi’an 710071, China
School of Computer Science, Xi’an Shiyou University, Xi’an 710065, China
2
is achieved [4]. Super-resolution SAR imaging can able to provide the fine and precise detection and recognition. Due to the existence of the three-dimensional velocity and the three-dimension
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